<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div id="app">
        <div v-once>
            {{msg}}
        </div>
    </div>
</body>
<script src="../../js/vue.js"></script>
<script>
    new Vue({
        el:"#app",
        data:{
            msg:"xxx"
        },
        mounted(){
            setInterval(()=>{
                this.msg +="x"
            },1000)
        }
    })
</script>
</html>